Support is sought for a one year study of infant social development and caretaking patterns in undisturbed free-ranging troops of langur monkeys, (Presbytis entellus) in Nepal. Detailed quantitative data will be collected on neonatal and young infant social activities and interactions; caretaking behaviors; and adult male and infant relations. These data are expected to yield normative profiles of neonatal and young infant social development and caretaking patterns, and will serve as a basis for evaluating various hypotheses concerning langur troop social factors, and infant development. This species of monkey provides a very different model of early development, caretaking, attachment and dependency that that of the well known baboon-macaque pattern. Multiple important caretakers provide the langur neonate with a wide variety of caretaking experiences from the day of birth. Continuous, daily observations of neonates and infants in free-ranging and undisturbed troops of langurs is proposed. Data will be collected through focal animal samples. The study is planned to permit integration of field and laboratory research. The research plan has been designed so that methods of data collection and data analysis have been standarized between the proposed study and ongoing research at Berkeley. This study will provide detailed field data, which hitherto have been unavailable. These data will aid in establishing the langur as an experimental animal by revealing exactly how different wild and captive social groups are, and will serve as a baseline for interpreting the generality and reliability of experimental findings in a laboratory situation. A substantial body of data on the proposed study troops exist as a result of nearly two years of observations on these wild langurs.